At least four people have been killed after one of the most powerful typhoons ever recorded hit the Philippines.

The victims of Super Typhoon Haiyan are reported to include a mother and child who drowned in South Cotabato, and a boy who was struck by lightning in Zamboanga City.

A fourth person was killed by a falling tree, according to the AP news agency.

Residents of Cebu City shelter from the storm's powerful winds

However, the number of confirmed deaths is expected to rise as emergency workers reach the worst affected areas, many of which remain cut off.

Minnie Portales, a spokesman for the aid agency World Vision, said: "As we wait for early reports from some of the hardest-hit provinces, we fear for the worst. This could be very bad."

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Gallery: Faces Of Storm's Brutal Aftermath

A man surveys felled trees in an area devastated by Typhoon Haiyan in Palo township.

Anna Lindenfors, Save the Children's director for the Philippines, added: "We expect the level of destruction caused by Typhoon Haiyan to be extensive and devastating, and sadly we fear that many lives will be lost."

Some 750,000 people living in villages in Haiyan's path were ordered to leave their homes amid fears the storm damage could be the worst in the Philippines' history.

Many of them are refugees whose homes were reduced to rubble when a 7.2 magnitude earthquake struck Bohol last month.

The typhoon, which is now careering across the South China Sea towards Vietnam, packed sustained winds of 195mph and gusts of up to 235mph, according to the US Navy's Joint Typhoon Warning Centre in Hawaii.

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Gallery: Satellite Views: Typhoon Haiyan

Typhoon Haiyan hits the Philippines in this weather satellite image, courtesy of the Japan Meteorological Agency.

On land, differing reports from meteorologists put the wind speeds at between 145mph and 170mph.

Jeff Masters, a former hurricane meteorologist who is a director at the private firm Weather Underground, warned there would be "catastrophic damage".

"There aren't too many buildings constructed that can withstand that kind of wind," he said. "The wind damage should be the most extreme in the Philippines' history."

The 300-mile-wide cyclone, known locally as Yolanda, whipped up waves that reached six metres high and threatened to inundate low lying areas.

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Local journalist Mike Cohen told Sky News there were already reports of some landslides and a "very strong storm surge" entering coastal towns and villages.

Up to 12 million people live in areas affected by the typhoon, including the tourist districts of Leyte Island and Borocay Island.

President Benigno Aquino III, who had threatened to use guns to force people living in high-risk areas to leave, put dozens of military planes, helicopters and ships on standby.

"No typhoon can bring Filipinos to their knees if we'll be united," he added.

Some meteorologists have claimed Haiyan is the strongest severe tropical storm ever to make landfall.

According to the Reuters and AP news agencies, the record is currently held by 1969 storm Hurricane Camillie, which had winds of up to 190mph.

Meteorologists fear the storm could intensify further as it approaches the Vietnamese coast, where it is expected to make landfall on Sunday morning.

Haiyan is the 24th tropical storm to hit the Philippines this year.

Last year, Typhoon Bopha, which had maximum sustained winds of 175mph, killed 1,100 people in the country.